High-tc superconducting ceramic oxide products and macroscopic and microscopic methods of making the same

ABSTRACT

High-Tc superconducting ceramic oxide products and macroscopic and microscopic methods for making such high-Tc superconducting products. Completely sealed high-Tc superconducting ceramic oxide products are made by a macroscopic process including the steps of pressing a superconducting ceramic oxide powder into a hollow body of a material inert to oxygen; heat treating the superconducting ceramic oxide powder packed body under conditions sufficient to sinter the ceramic oxide powder; and then sealing any openings of the body. Optionally, a waveform or multiple pulses of alternate magnetic field can be applied during the heat treatment. The microscopic method of producing a high-Tc superconducting ceramic oxide product includes the steps of making a high-Tc superconducting ceramic oxide thin film; optionally sintering the deposited thin film in a magnetic field; and removing partial oxygen content of the thin film by a scanning tunneling electron treatment machine to form a microscopic insulation layer between two high-Tc superconducting domains of the thin film.

BACKGROUND OF THE INVENTION

The present invention relates to high-Tc superconducting ceramic oxideproducts, and macroscopic and microscopic methods for making suchhigh-Tc superconducting products. The high-Tc superconducting ceramicoxide products of the present invention have a high critical currentdensity, high critical magnetic field, long life and are capable ofbeing recharged or having superconductivity regenerated.

Since the initial discovery of high-Tc superconductivity in metal-oxideceramics, many people have tried to determine the underlying physicalorigin of this superconductivity. It is generally agreed that themicrostructure of the CuO₂ plane of high-Tc superconductors plays a keyrole in high-Tc superconductivity. Viewed in two dimensions, there arefour oxygen atoms around a single Cu atom in high-Tc metal-oxidesuperconducting ceramics (in three dimensions, there would be six oxygenatoms around one Cu atom), and each Cu atom can supply at most threeelectrons to its nearest neighbors. This means that there can be nostable valence bond between the Cu atoms and the oxygen atoms. The Cuelectrons are, therefore, only weakly localized and can pass across theoxygen bridges to complete quantum tunneling. Such collective quantumtunneling plays the key role in the high-Tc superconductivity. Since theexchange interaction between the two Cu ions is mediated via the oxygenions, the extra spin of a hole localized on the oxygen will have a bigeffect. Designating the two Cu ions spins by S₁ and S₂, and the 0 by σ,the σ would prefer to be parallel or antiparallel in respect to both S₁and S₂. The spins of high-Tc superconductors are, therefore, verydisordered. The local spin wavefunction is either symmetric orantisymmetric and is rapidly changing with time, because of the mixedvalence resonance vibration. The disordered spin wavefunction will beautomatically adjusted to accompany the tunneling electrons.

The present invention relates to new methods of making completely sealedhigh-Tc superconducting products using metallic oxide ceramics, and tothe completely sealed high-Tc superconducting products produced thereby.The inventive methods and products are based on the realization that theoxygen content of the metal-oxides plays an important role in high-Tcsuperconductors and products incorporating the same. Below a criticaloxygen content X₁ (O), or above a critical oxygen content X₂ (O),superconductivity is destroyed. The transitin temperature Tc changes inbetween these critical concentrations. For example, for thesuperconducting oxide system YBa₂ Cu₃ O_(X), X_(c1) (O)=6.5 and X_(c2)(O)=7.0. Experiments show that if oxygen atoms escape from high-Tcsuperconductors, thereby lowering the oxygen content to less than thecritical oxygen content X_(c1), the superconductivity of the metal-oxideis destroyed. If the oxygen content is then increased, for example bysintering the oxygen-depleted metal-oxide ceramic within a predeterminedtemperature range in the presence of oxygen, the superconductivity willbe restored. The principal point is that for YBa₂ Cu₃ O_(X)superconductors, the oxygen content X(O) must satisfy the equation6.5<X(O)<7.0, and for all high-Tc oxide superconductors the oxygencontent X(O) must satisfy the equation X_(c1) <X(O)<X_(c2).

The high-Tc superconductivity state of oxide ceramics is only ametastable state, and the superconductive oxide ceramics will tend tolose oxygen to become a stable state insulator. This process of oxygenloss may take a few hours, a few days, a few months, or even a few yearsor longer depending upon the conditions surrounding the superconductiveoxide including temperature, atmosphere, and the like. However,regardless of how long tee oxygen loss process may take, the tendency ofthe metastable superconductive state to change to the stable insulativestate is certain. Therefore, to protect the high-Tc superconductivity ofoxide ceramics, the oxygen content of the ceramic corresponding to thesuperconductive state must be maintained.

The present invention provides a completely sealed superconductingproduct whereby the oxygen loss is prevented and a long-lived high-Tcsuperconducting ceramic oxide product is attained. As described indetail, hereinafter, the seal can be made using metal, plastic or anymaterials which are inert to oxygen.

The present invention is also based on the recognition that the high-Tcsuperconductors are ceramic materials, a basic property of which isbrittleness. Because of this brittle characteristic of ceramicsuperconductors, many attempts were made to produce high-Tcsuperconducting ceramic products using traditional methods to makewires, cables, tapes and the like, and then making superconductingproducts from the superconducting ceramic-containing wires, cables andtapes. Examples of such wire, cable and tape methods of producingsuperconducting ceramic products include: U.S. Pat. No. 4,952,554; U.S.Pat. No. 4,965,249; U.S. Pat. No. 4,975,416; and U.S. Pat. No.4,973,574. Other methods of making superconducting ceramic products areshown, for example, in the following U.S. Patents: U.S. Pat. No.4,975,411; U.S. Pat. No. 4,975,412; U.S. Pat. No. 4,974,113; U.S. Pat.No. 4,970,483; U.S. Pat. No. 4,968,662; U.S. Pat. No. 4,957,901; U.S.Pat. No. 4,975,414; and U.S. Pat. No. 4,939,121.

However, all of these prior attempts to make high-Tc superconductingceramic oxide products suffer from one or more disadvantages. The wireand cable making methods typically include a drawing or working step toreduce the diameter of the superconducting ceramic oxide product. Suchdrawing and working steps are liable to break the brittle ceramic oxideproduct, therefore the breaking and sintering cycles will repeat againand again and the resulting wires have poor flexibility anddiscontinuity caused by breaking. Further, prior attempts to producesuperconducting ceramic products have not had the high mass densitynecessary to achieve high current density, have had an insufficientratio of superconducting cross-sectional area to non-superconductingcross-sectional area, and have suffered undesirable oxygen lossresulting in loss of superconductivity. In addition, prior methods ofmaking high-Tc superconducting ceramic oxide products have been costly,involving expensive materials and numerous, time consuming steps, andhave produced products of only limited shapes suitable for only limitedapplications. Also, prior methods could not, or could not easily, makehigh-Tc superconducting connections, which is necessary, especially formaking a high-Tc superconducting magnet. A key technology for makinghigh-Tc superconductive magnets is the making of zero resistanceconnections.

This invention also attempts to apply an alternate or a selectivewaveform pulse magnetic field to destroy the magnetic moment order(which does not do good to the high-Tc superconductivity), to accelerateoxygen to occupy the positions of CuO₂ planes, and to orient the CuO₂plane to a desired direction by the dynamic process of the alternatefield during the heat treatment. This invention using a dynamic fieldhas high efficiency compared with a static magnetic field. This isbecause ##EQU1## is magnetization and H(t) is alternate field. Thedynamics is very important; therefore, alternate field will rapidlyrotate magnetic moment randomly, and create the condition to accelerateoxygen to occupy position on CuO₂ plane, because AF local magnetic orderresists diffusion of oxygen. Therefore, the applied alternate field ismuch better than an applied static magnetic field.

SUMMARY OF THE INVENTION

The present invention relates to high-Tc superconducting ceramic oxideproducts and to macroscopic and microscopic methods of making suchproducts. The superconducting ceramic oxide used to produce thesuperconducting products of the invention can be any superconductingceramic oxide (including the Al oxide family) and, for example, is anREBa₂ Cu₃ O₉₋δ ceramic, wherein RE is one or more rare earth elementsfrom the group Y, La, Eu, Lu and Sc, and δ is typically in the rangefrom 1.5 to 2.5. One specific ceramic oxide for use in the products ofthe present invention is YBa₂ Cu₃ O_(X), wherein X is between 6.5 and7.0.

The high-Tc superconducting ceramic oxide product of the presentinvention are produced such that oxygen loss is minimized orsubstantially prevented and the superconducting properties of theceramic oxide products are maintained for a substantial, evenindefinite, period of time. One method for producing a superconductingceramic oxide product according to the present invention is amacroscopic method of producing completely sealed high-Tcsuperconducting ceramic oxide products. This macroscopic methodcomprises the steps of making a superconducting ceramic oxide powder;providing a hollow body of a material which does not react with oxygen;pressing the superconducting ceramic oxide powder into the hollow bodyat a net pressure of at least from 5 ×10⁴ psi to 1×10⁷ psi, preferablyat least 1.2×10⁵ psi for YBa₂ CuO_(x) (the pressure will depend upon thematerial and shape); heat treating the body with the superconductingceramic oxide powder pressed therein in an oxygen atmosphere attemperatures and for time periods of sintering, annealing and coolingwhich are sufficient for sintering the ceramic oxide powder; optionallyapplying a waveform or multiple pulses of alternate magnetic field (from0.0001 Tesla to 300 Tesla) during the sintering and subsequent heattreatment procedure to dynamically destroy local magnetic moment anddynamically accelerate oxygen to occupy positions in the CuO₂ planes anddynamically to orient the microscopic CuO₂ plane to desired direction tocarry high critical current and high critical field, the applied fieldstrength varying with the material and the shape of the products; andthen sealing the ends of the body and/or any other openings which mayhave been formed in the body prior to sintering. Local heat treatmentcan also be used to make connections between high-Tc superconductingproducts or a product and superconducting lead. If the superconductingceramic oxide product has a complicated shape, connections betweenhollow bodies having the superconducting ceramic oxide powder pressedtherein are joined and then a second pressing step is performed toensure that all connections are filled with superconducting powdercontinuously without any gaps before sintering.

The completely sealed high-Tc superconducting ceramic oxide productsproduced by the macroscopic method of this invention may be of anydesired shape and size and are suitable for use as high-Tcsuperconducting magnets, high-Tc superconducting motors, high-Tcsuperconducting generators, high-Tc superconducting transportationlines, high-Tc superconducting electric energy storage devices, orcomponents thereof, and, in general, may be used for any purpose whichrequires a superconductor.

The microscopic method of producing a high-Tc superconducting ceramicoxide product of the present invention is also based on the isolation(or "sealing") of a superconducting ceramic oxide composition to preventoxygen loss or diffusion and the resultant loss of superconductivity.The inventive microscopic method of making high-Tc superconductingceramic oxide products comprises the steps of: making a high-Tcsuperconducting ceramic oxide thin film on a substrate in situoptionally an alternate magnetic field can be applied during the makingprocess in situ by molecular beam deposition, molecular beam deposition,sputtering deposition, laser ablation or any other suitable means, andoptionally then sintering the deposited thin film in a magnetic field inan oxygen atmosphere, if necessary; and removing partial oxygen contentby a scanning tunneling electron treatment machine (STETM) from amicroscopic domain, e.g., 5Å to 1000Å, of the superconducting ceramicoxide thin film to form a microscopic insulation layer between twohigh-Tc superconducting domains which form a Josephson junction. High-Tcsuperconducting products made by the microscopic method of the presentinvention are particularly useful as high-Tc superconducting chips,high-Tc superconducting electric circuits, SQUIDS, and componentsthereof.

Therefore, it is an object of the present invention to provide high-Tcsuperconducting ceramic oxide products which do not suffer from thedisadvantages of prior superconducting ceramic products.

Another object is to modify a scanning tunneling microscope machine to aSTETM, that is, from a microscopey to an electron treatment machine formaking microscopic patterns as desired by localized electric current andwhich not only can be used to produce high-Tc superconducting productsbut also can be used in the semiconductor industry.

Another object of the present invention is to provide high-Tcsuperconducting ceramic oxide products which are sealed to preventoxygen loss and loss of superconductivity.

Still another object of the present invention is to provide amacroscopic method for making high-Tc superconducting ceramic oxideproducts which does not require conventional wire and cable makingtechniques such as drawing and cold working.

It is still another object of the present invention to provide amacroscopic method for making high-Tc superconducting ceramic oxideproducts of a variety of shapes, sizes and configurations.

Yet another object of the present invention is to provide a method formaking high-Tc superconducting ceramic oxide products whereby thesuperconducting ceramic oxide compositions are mechanically,electrically and chemically protected.

A further object of the present invention is to provide macroscopic andmicroscopic methods for producing high-Tc superconducting ceramic oxideproducts of high quality and having a long life.

Still a further object of the present invention is to provide amicroscopic method for producing high-Tc superconducting ceramic oxideproducts.

Yet a further object of the present invention is to provide an apparatusand method for forming microscopic insulating layers or domains within asuperconducting ceramic oxide thin film.

Another object of the present invention is to provide a method formaking continuous superconducting connections between high-Tcsuperconducting products.

Another object of the present invention is to provide a method usingalternate magnetic field during the heat treatment procedure forproducing superconducting products, in order to destroy local magneticmoment, to accelerate oxygen to occupy CuO₂ plane position, and toorient CuO₂ plane to desired orientation dynamically.

These and other objects of the present invention will be furtherunderstood by reference to the following detailed description anddrawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a first embodiment of a sealed,high-Tc superconducting ceramic oxide product produced by themacroscopic method of the present invention;

FIG. 2 is a cross-sectional view of a second embodiment of a sealed,high-Tc superconducting ceramic oxide product (high-Tc superconductingmagnet) produced by the macroscopic method of the present invention;

FIG. 3 is an exploded, cross-sectional view of the components forproducing the superconducting product (high-Tc superconducting magnet)shown in FIG. 2;

FIG. 4 is a cross-sectional view of a third embodiment of a sealed,high-Tc superconducting ceramic oxide product produced by themacroscopic method of the present invention;

FIG. 5 is a cross-sectional view of a sealed connection, taken alongline V--V of FIG. 4;

FIGS. 6a, 6b and 6c are cross-sectional views of embodiments of thehigh-Tc superconducting ceramic oxide products of the present inventionhaving different shapes;

FIG. 7 is a cross-sectional view similar to FIG. 1, showing differentend seal connections;

FIG. 8a and FIG. 8b are schematic illustrations of the sintering of ahigh-Tc superconducting ceramic oxide macroscopic product and thin film,respectively, in an alternate magnetic field according to themacroscopic and microscopic methods of the present invention,respectively;

FIGS. 9, 10 and 11 are schematic illustrations of modified scanningtunneling machines, hereinafter referred to as STETMs (scanningtunneling electron treatment machines) useful in the microscopic methodof the present invention;

FIG. 12 is a schematic cross-sectional view of a high-Tc superconductingceramic oxide film provided with low oxygen content insulating domainsproduced by the microscope method of the invention;

FIG. 13 is a schematic illustration of a SQUID made by the microscopicmethod of the invention;

FIG. 14 is a schematic illustration of an integrated circuit made by themicroscopic method of the invention; and

FIG. 15 is a schematic illustration of ceramic powder-containing hollowbody in a casing suitable for pressurizing in accordance with thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawing figures, and in particular FIGS. 1-7, thereare shown several embodiments of a completely sealed, high-Tcsuperconducting ceramic oxide product of the present invention. Each ofthese embodiments is made by the macroscopic method of the invention. Toproduce the completely sealed superconducting products of FIGS. 1-7, thefollowing macroscopic method is used.

First, the compounds or ingredients for making a high-Tc superconductingceramic oxide composition are mixed together in powder form, by standardpowder metallurgical techniques. For example, high purity Y₂ O₃, BaCO₃and CuO powders are mixed together, without water content, to make thepreferred high-Tc superconducting composition YBa₂ Cu₃ O_(x). Then, themixed powder is heated up to 940° C. in an unglazed ceramic crucible ina well ventilated oven for about 12 hours, and then cooled over a periodof about 3 hours. The powder mixture is then kept at a temperature ofabout 450° C. for another about 3 hours and then cooled slowly to roomtemperature. After pulverizing and mixing the resultant powder, the sameprocedure is repeated for another 6 to 12 hours, with oxygen flowingthrough the oven. This procedure produces a high-Tc superconductingblack colored powder. The powder is then reground a third time.

This superconducting powder is then used in the macroscopic method ofthe present invention as follows. The superconducting powder is pressedinto a tube or preform made of any suitable material which does notreact with oxygen. The tube or preform may be made of a metal which doesnot react with oxygen or a plastic material. Examples of suitablematerials are stainless steel and stainless steel tubes having an innerwall coated with a material inert to oxygen. A pressure sufficient toobtain a net pressure greater than about 5×10⁴ psi is applied to thesuperconducting powder to ensure that the powder is completely pressedinto the tube or preform with no vacant volume. The applied pressure isselected to ensure that the desired density of the packed powder isobtained. For example, to obtain a density of about 5.0 grams/cm³ of aYBa₂ Cu₃ O_(x) powder, an applied pressure of 1.2×10⁵ psi is used. Thisnet pressure can be achieved using a mechanical press, liquid press,high pressure 895 press and any high pressure technique can be used. Toguarantee the required high net pressure, the packed tubes should besurrounded by a solid metal base such as surrounding base 200 shown inFIG. 15, very similar to the solid metal model for casting. The tube orpreform having the packed superconducting powder therein, with the endsof the tube or preform being open, is then sintered as follows. Thepacked tube or preform is heated in a furnace or oven from roomtemperature to 940° C. over a period of about 3 hours and then ismaintained at a temperature of about 940° C. in air for about 6 hours.An O₂ flow is then started through the oven or furnace and the sample isgradually cooled to 550° C. over a period of about 10 hours, and then iscooled to a temperature of about 200° C. over another period of about 10hours while maintaining the O₂ flow, and then slowly to roomtemperature, again with the O₂ flow, over another 10 hour period oftime. If the preform is a complicated shape rather than a simple tube,apertures may be opened in the preform in addition to the open endsthereof, to guarantee oxygen flow through the entire product. Theseapertures are resealed after sintering is completed.

The thus sintered product is then tested for zero resistance and for theMeissner effect. The sintered product thus having demonstratedsuperconductivity, the ends of the tube or preform are sealed to preventoxygen los and complete production of the completely sealed high-Tcsuperconducting ceramic oxide products of the present invention.

With more particular reference to the drawing figures, the completelysealed high-Tc superconducting product 10 of FIG. 1 is produced asfollows. A superconducting ceramic oxide powder 12 is pressed into atube 14 at a pressure greater than 1.2×10⁵ psi; the packed tube is thensintered in an oxygen atmosphere as detailed above, preferably with theoxygen flowing at a rate greater than 1 atmosphere; and then end seals16, 18 are applied to the open ends of the tube 14 of the sinteredproduct to effect the complete seal. An alternate magnetic field can beapplied during the heat treatment period as shown in FIG. 8a. Prior tosealing the ends of the tube 12, the high-Tc superconducting propertiesof the product are verified or determined as discussed above. The endseals 16, 18 may be applied by any known means which are effective toensure a fluid tight seal, for example, welding or screw sealing endcap.The tube 14 may have any desired cross section, such as circular,rectangular or square, depending upon the desired end use of thesuperconducting product. Local heating can be used to makesuperconducting between superconducting products or leads, under certainpressures and in oxygen or air environment, electrical heating or anyother local heating can be used.

The macroscopic process of the present invention also provides a simplemethod for producing high-Tc superconducting ceramic oxide products ofvarious shapes, including complicated and composite shapes, asillustrated in FIGS. 2-6c. FIGS. 2 and 3 illustrate, respectively, ahigh-Tc superconducting magnet produced according to the presentinvention, and the component parts thereof. The high-Tc superconductingmagnet shown in FIG. 2 provides a complete, continuous superconductingloop without any welding, soldering or pressing joints after making. Toproduce the superconducting magnet product 20 shown in FIG. 2, twometal, preferably stainless steel, tubes 22, 24, which do not react withoxygen, are provided and tube 22 is wound into an appropriate oxide 26,in powder form, is pressurized at a pressure of at least 1.2×10⁵ psi ineach of the metal tubes 22, 24. It is to be understood that the steps ofshaping the metal tube into a desired configuration and pressurizing thepowder thereinto can be reversed. That is, the metal tube can be shapedinto a desired configuration after at least a portion of thesuperconducting ceramic oxide powder has been pressurized therein. Afterthe superconducting ceramic oxide powder has been pressurized into eachof the metal tubes 22, 24, the tubes 22, 24 are assembled, as shown inFIG. 3, to form the desired complicated shape of the superconductingmagnet 20. Metal tube 24 is joined to metal tube 22 by any suitablemeans, such as by welding or any other tube connection method.

After the metal tubes 22, 24 have been joined the powder is againpressurized under a pressure greater than 50K psi (5×10⁴ psi<P<1×10⁷psi) to make a continuous connection without any gap in the entiretubular structure of the product, to safeguard against gaps between tube22 and tube 24 and potential oxygen loss. This repressurizing of thesuperconducting ceramic oxide powder ensures that there is a continuousconnection through the joints where the subparts, i.e., metal tubes 22,24, have been joined to make the final shape.

Then, the preform having the packed superconducting powder therein issintered, as described above, in an oxygen atmosphere. For a complicatedshape such as that of the superconducting magnet shown in FIG. 2, it ispreferable that some apertures or windows be opened in the metal tubes22, 24 to ensure that oxygen flows throughout the entire body. After thehigh-Tc superconducting properties of the sintered product have beenchecked, the product is completely sealed by resealing the apertures orwindows, if any, and completely sealing the ends of the metal tube 26with endcaps 28, 29.

Referring now to FIGS. 4 and 5, there is shown a superconducting ceramicoxide product made by joining or connecting, in end-to-end relation, twosintered products similar to the sintered product 10 shown in FIG. 1.More particularly, as shown in FIG. 4, two sintered products, eachhaving a tube 32 with sintered superconducting ceramic oxide powder 34pressed therein and sealed at one end with an endcap 36 are joined byconnector 38. Connector 38 surrounds the adjacent ends of the tubes 32and the connector 38 is held together using screws 39, as shown in FIG.5. Alternatively, or in addition to the screws 39, the connector 38 maybe provided with internal threads and the ends 40 of the tubes 32 may beprovided with mating screw threads so that the ends 40 of the metaltubes 32 may be screwed into connector 38.

FIGS. 6a, 6b and 6c show additional shapes of sintered products whichmay be made by the macroscopic method of the present invention, asdescribed above. High-Tc superconducting ceramic oxide product 50 ofFIG. 6a, comprises of a tube 52 having sintered superconducting ceramicoxide powder 54 pressed therein and having endcaps 56, 58 provided onthe ends of the tube 52. Superconducting ceramic oxide product 50 ismade by the macroscopic method described above. In making this product,the tube 52 may be bent to the 90° angle shown before or afterpressurizing of the powder 54 therein. Hi-Tc superconducting ceramicoxide product 60 shown in FIG. 6b has a T-structure which isparticularly suitable for making T-connections in superconductingproducts. The T-superconducting ceramic oxide product 60 shown in FIG.6b comprises a metal tube 62, sintered superconducting ceramic oxide 64and endcaps 66, 67 and 68. The T-shaped superconducting product 60 canbe made by providing a tube, such as a metal tube, having a T-shape orby joining two straight tubes, as discussed with respect to FIGS. 2 and3, to form the T-shaped structure.

Finally, FIG. 6c shows a completely sealed, four-way superconductingconnector produced by the macroscopic method of the present invention.The four-way connector 70 comprises a tube 72, a sinteredsuperconducting ceramic oxide 74 and endcaps 76, 77, 78 and 79. Thefour-way superconducting connector 70 can be made by providing afour-way tube or by joining two tubes on centrally and substantiallyopposite on another on opposite sides of a single tube to form acontinuous superconducting four-way connector.

Referring now to FIG. 7, there is shown an alternate method of sealingthe ends of a tube containing a sintered high-Tc superconducting ceramicoxide. The superconducting product 80, shown in FIG. 7, comprises a tube82, a sintered superconducting ceramic oxide 84, an endcap 86 and an endsealing means 88. A first end 90 of the tube 82 is provided withinternal threads which matingly engage endcap 86, which endcap is afemale screw connector. End 92 of tube 82 is provided with internalthreads and matingly engages female screw connector 88.

Although several different embodiments of a superconducting ceramicoxide product produced by the macroscopic method of the presentinvention have been described in detail above, it is to be understoodthat other shapes, configurations and sealing arrangements arecontemplated within the scope of the present invention. In addition,modifications to the macroscopic process described in detail above maybe made as necessary to adapt the process to superconducting ceramicoxides other than those specifically disclosed. Further, additionalprocess steps may be employed together with the steps of the macroscopicprocess detailed above. For example, the sintering of thesuperconducting ceramic oxide powder may be conducted in an alternatemagnetic field (10⁻⁴ Tesla to 300 Tesla), as shown in FIG. 8a, to ensurehigh current density. Further, after long time use of thesuperconducting ceramic oxide products of the present invention, theseproducts can be resintered in an oxygen atmosphere and resealed so thatthey can be used for another lengthy period of time.

Referring now to FIGS. 8b-14, the microscopic method of the presentinvention, and the superconducting ceramic oxide products producedthereby will be explained. The microscopic method comprises the stepsof: forming a thin film of a high-Tc superconducting ceramic oxidecomposition by a known deposition technique such as electron beamdeposition, sputtering deposition, molecular beam deposition, laserablation or any other suitable method, optionally with an alternatemagnetic field being applied during the film making process in situ orduring the sintering process after the film making to upgrade thequality of the thin film; and removing partial oxygen content from amicroscopic domain of the thin film superconducting ceramic oxide bywarming up the microscopic domain using a modified scanning tunnelingmicroscope referred to hereinafter as a STETM (scanning tunnelingelectron treatment machine). Before STETM treatment, the insulatorsubstrate upon which the thin film is initially formed must be removed,and then the high-Tc film supports itself or is coated with a supportiveconductive layer. After the STETM treatment, the thin film is sealedwith a suitable sealing layer to protect the oxygen content and make itstable. The potential barrier will protect the separation of the lowoxygen domain and the high oxygen domain. If a thin conductive substrateis used for the thin film making, it need not be removed before STETMtreatment.

The thin film as deposited can be superconducting or, optionally, thethin film can be sintered under conditions very similar to thosedescribed above with respect to the macroscopic methods, in order toproduce a high-Tc superconducting thin film. Preferably, such sinteringtakes place in an alternate magnetic field as illustrated in FIG. 8b.The required characteristics of the magnetic field are alternatemagnetic field waveforms in the range from 10⁻⁴ Tesla to 300 Tesla. Ifthe thin film is deposited on a substrate, the substrate may be of anysuitable dimension, e.g., from 10⁻⁶ m to 1 cm to in thickness. Thesubstrate can be any oxide material except a CuO system. For example,the substrate could be an AlO or MgO system. The thin film generally hasa thickness of from about 30Å to about 10 μm, preferably between about100Å and 1000Å.

The STETM useful in practicing the microscopic method of the presentinvention is a modified STM having two tips opposite one another asshown in FIGS. 9 and 10, or having two opposed boards, each providedwith a plurality of opposed tips as shown in FIG. 10. AC or DC currentis passed between the opposed tips to locally heat up a microscopicdomain having a size from about 5Å to about 1000Å. In the presentinvention, a thin high-Tc superconducting oxide film is held between thetwo tips or two boards of tips. When two tips are close to the film, theAC or DC current passing through the tips turns on a local domain ofabout 5 to 20Å², to heat the thin film locally thereby removing oxygencontent locally as desired. The opposed tips can be moved independentlyof one another or together with one another, as determined by a programcontrolling such movement. Although FIGS. 9-11 show a DC current source,it is to be understood that an AC current source could be substitutedtherefor. The current can be from about 10⁻⁶ Amps to about 100 Amps,depending on the type and thickness of the thin film and any supporting(conductive) substrate. The microscopic domain is heated to atemperature of between 200° and 900° C. in an argon atmosphere to removethe oxygen content of that microscopic domain and form a microscopicinsulating domain.

The microscopic method of the present invention enables one or moremicroscopic insulating domains each having a size of between about 5Åand 1000Å to be formed in the superconducting ceramic oxide thin film.The microscopic insulating layers or domains between the high-Tcsuperconducting domains form Jospehson junctions for SQUIDS or anyhigh-Tc superconducting electric circuit. Compared to a 5000Å insulationin a semiconductor, high-Tc superconducting microscopic circuitsproduced by the present invention can save space by a factor of 10² ×10²×10² for 3D circuits and 10⁴ for 2D circuits.

After the STETM treatment, the microscopic insulation layer is in astable state and the adjacent superconducting domains are in ametastable state, and therefore, a potential barrier of oxygen moleculeis established between the two states. The microscopic film contains thesuperconducting domain and the insulator domain in then completelysealed by applying a suitable coating sealing layer over the film, suchas the sealing layer shown in FIG. 12. After wire connections areapplied to the thin film structure as desired, the whole film is sealedexcept the wire. Therefore, the film, which contains superconducting andnonsuperconducting domains, will be sealed by the coating sealing layer.The O₂ content and the domain separations are thus protected by thesealing for long life. The oxygen content of the superconducting domainhas nowhere to go because diffusion to the insulation domain requiresexcitation energy, which forms a potential barrier to separate thesuperconducting and insulating domains. Therefore, the sealed high-Tcsuperconducting chips exhibit long life. Liquid nitrogen or low noiserefrigeration will guarantee the operation of the high-Tcsuperconducting circuits.

Referring now to FIG. 8b, there is shown the sintering of asuperconducting thin film ceramic oxide in an alternate magnetic field.The thin film 100 is sintered in furnace 102 in an oxygen atmosphere,with oxygen flowing into the furnace 102 through conduit 104. Aalternate magnetic field is applied in the B direction by magnetsolenoids 106.

FIG. 9 schematically illustrates the STETM treatment of superconductingthin film ceramic oxide 110 in accordance with the microscopic method ofthe invention. The thin film 110 is supported by support 112 such thatthe thin film 110 is substantially perpendicular to pins 114, 116 of theSTETM. Pins 114, 116 are connected to electric current source 118, thepin 114 having a negative potential and pin 116 having a positivepotential or an alternate AC potential. Each of the pins 114, 116 issupported by three mutually perpendicular or orthogonal piezoelectricsticks 120, extending in the X, Y and Z directions. The pins can moveindependently or dependently by programming as desired. The current canbe 10⁻⁶ Amp to 100 Amp. Voltage can be 10⁻³ to 10⁴ V, depending on thematerial, thickness and the like. Treatment by a pair of opposed pinscan be localized to 5Å² or even smaller, and treatment by opposed boardseach having a plurality of pins can be as large as 1 μm². The tips andboards can be made of tungsten, platinum, gold, and compounds thereof,as well as other suitable materials.

FIG. 10 schematically shows the flow of electrons 122 from the negativepin 114 to the positive pin 116 through the superconducting thin film110 to remove oxygen content and form the microscopic insulating domain.FIG. 11 shows an alternative embodiment of the STETM wherein a pluralityof opposed positive pins 126 and negative pins 124 are provided tosimultaneously form a plurality of microscopic insulating domains in thethin film superconducting ceramic oxide 128.

FIG. 12 illustrates a superconducting thin film ceramic oxide product130 produced by the microscopic method of the present invention. Thesuperconducting thin film ceramic oxide product 130 comprises aplurality of microscopic insulating domains 132 between adjacent high-Tcsuperconducting domains 134. A sealing layer 136 is provided around thesuperconducting thin film ceramic oxide to prevent loss of oxygen fromthe superconducting domains and to prevent the resultant loss ofsuperconductivity and protect the separation between the superconductingand nonsuperconducting domains. Because the potential barrier is sealedand isolates the areas surrounding it, no excitation energy can beprovided to overcome the potential barrier and the superconductivitycircuit has a long lifetime. The sealing layer is an insulating coatinglayer which is inert to oxygen and can be applied by any suitable means,such as spraying, coating, immersion, and the like. 137 are wireconnections.

Finally, FIGS. 13 and 14 illustrate, respectively, a SQUID 150 made bythe microscopic method of the present invention and an integratedcircuit 160 made by the microscopic method of the invention. Morespecifically, FIG. 13 shows a SQUID 150 having a high-Tc superconductingloop 152 and a Josephson junction 154 which can be as small as 5Å-20Å(i.e., close to the coherence length of about 5Å on CuO₂ plane) formedby the microscopic insulating domain. The microscopic process of thepresent invention is unique in that it can make such small and accuratehigh quality SQUIDs. The SQUID of FIG. 13 is made from a high qualityhigh-Tc superconducting film. The film is held in the STETM and asuperconducting ring is masked. The remainder of the film are is treatedby the STETM to remove oxygen content and form an insulting area ordomain. A Josephson junction is then made by the STETM treatment of thedesired areas of the remaining superconducting ring. A wire connection170 is then made and the whole film structure is sealed except the wireconnection.

FIG. 14 shows an integrated circuit 160 comprising insulating layers ordomains 162 and high-Tc superconducting domains 164. The integratedcircuit 160 is similarly made by treating a thin high-Tc superconductingfilm with the STETM to produce a desired pattern of insulating domains164 and superconducting domains 162; affixing wire connections 174 tothe resultant structure; and then sealing the structure with theexception of the wire connections.

The description of the preferred embodiments contained herein isintended in no way to limit the scope of the invention. As will beapparent to a person skilled in the art, modifications and adaptationsof the structure and method of the above-described invention will becomereadily apparent without departure from the spirit and scope of theinvention, the scope of which is described in the appended claims.

What is claimed is:
 1. A method of making a high-Tc superconductingproduct useful as a high-Tc superconducting magnet comprising acontinuous close loop and having zero electrical resistance in saidcontinuous closed loop, said method comprising the steps of:providing afirst hollow body of a material inert to oxygen; providing a secondhollow body of a material inert to oxygen; pressing a high-Tcsuperconducting ceramic oxide powder into said first hollow body andsaid second hollow body; and then joining said first hollow body withsaid high-Tc superconducting ceramic oxide powder pressed therein tosaid second hollow body having said high-Tc superconducting ceramicoxide powder pressed therein, thereby forming a continuous loop definedwithin said first and second hollow bodies; and then repressing saidhigh-Tc superconducting ceramic oxide powder in the joined first andsecond hollow bodies thereby making a continuous connection through thejoints at which said first and second hollow bodies are joined; and thenheat treating the joined first and second hollow bodies with the pressedhigh-Tc superconducting ceramic oxide powder therein, with an end of atleast one of said first and said second hollow bodies being open, theheat treating being conducted in an oxygen atmosphere at sufficienttemperatures and for time periods such that the high-Tc superconductingceramic oxide powder is sintered annealed, and cooled; and then sealingthe open end of said at least one of said first and said second hollowbodies, thereby preventing oxygen loss; wherein the step of heattreating the joined first and second hollow bodies is the only heatingof the pressed high-Tc superconducting ceramic oxide powder and thehigh-Tc superconducting ceramic oxide powder pressed in the first andsecond hollow bodies is not heated prior to joining the first and secondhollow bodies.
 2. The method according to claim 1, wherein the pressingof the high-Tc superconducting ceramic oxide powder into said firsthollow body and said second hollow body is at a net pressure of from5×10⁴ psi to 1×10⁷ psi.
 3. The method according to claim 1, wherein thehigh-Tc superconducting ceramic oxide powder is YBa₂ Cu₃ O_(X) and thepressing of the high-Tc superconducting ceramic oxide powder into saidfirst hollow body and second hollow body is at a pressure of at least1.2×10⁵ psi.
 4. The method according to claim 1, wherein the high-Tcsuperconducting ceramic oxide powder is YBa₂ Cu₃ O_(X), and wherein X isbetween 6.5 and 7.0.
 5. The method according to claim 1, wherein therepressing of the high-Tc superconducting ceramic oxide powder in thejoined first and second hollow bodies is at a pressure greater than5×10⁴ psi.
 6. The method according to claim 1, wherein the repressing ofthe high-Tc superconducting ceramic oxide powder in the joined first andsecond hollow bodies is at a pressure between 5×10⁴ psi and 1×10⁷ psi.7. The method according to claim 1, further comprising the step ofsurrounding the joined first and second hollow bodies by a solid metalbase, wherein the repressing of said high-Tc superconducting ceramicoxide powder in the joined first and second hollow bodies is performedwith the joined first and second hollow bodies surrounded by said solidmetal base.
 8. The method according to claim 1, further comprising thestep of testing the high-Tc superconducting properties of the joinedfirst and second hollow bodies with the pressed high-Tc superconductingceramic oxide powder therein after heat treating and before sealing theopen end thereof.